A method for obtaining a molded article by molding by injection a pellet composed of a thermoplastic resin and a reinforcing fiber is generally used.
However, when an injection-molding method is employed, there occurs a problem in which reinforcing fibers are broken and shortened during the process of injection molding, and thus the reinforcing effect is deteriorated.
Patent Literature 1 (JP-B 3631994) and Patent Literature 2 (JP-B 4743592) disclose an invention wherein a press molding method is employed instead of an injection molding method.
Patent Literature 1 discloses an invention of a long-fiber-reinforced thermoplastic resin (hereinafter, referred to as L-FRTP) sheet, wherein wire rods, each of which has a width of from 0.2 to 5 mm and a length of from 10 to 150 mm and is made of an unidirectionally L-FRTP, are oriented at random and fixed together at intersections thereof, and the sheet has a basis weight of 30 to 500 g/m2 and a thickness of 0.1 to 1 mm and is provided with openings therein; and also an invention of a composite structure, wherein the L-FRTP sheet is arranged on at least one surface or an interior of a specific base material.
The section for Advantages of the Invention (paragraph 0051) describes that the surface rigidity of an L-FRTP sheet can be improved.
Patent Literature 1 describes that the L-FRTP has a circular or elliptical cross-sectional shape, and a long diameter/short diameter ratio of the cross-section is 3 or less (paragraph 0016). However, those used in the Example are only L-FRTP having a circular cross-sectional shape and not L-FRTP having an elliptical cross-sectional shape. This means that Patent Literature 1 discloses that those with a circular cross-section are preferred to obtain the advantages of the invention.
Patent Literature 2 discloses an invention of a long fiber reinforced thermoplastic resin linear molding material and a method for producing a long fiber reinforced thermoplastic resin molded article (Claims).
Regarding the cross-sectional shape of the long fiber reinforced thermoplastic resin linear molding material, Patent Literature 2 describes that “(a) The cross-sectional shape is close to a circle or an ellipse. This makes it easy to spray the linear molding material in a three-dimensional orientation, and press-molding of thus sprayed material can provide a sheet material or a molded article having reinforcement fibers oriented in a three-dimensional manner (paragraph 0028).” However, the Examples, Reference Examples and Comparative Examples thereof do not refer to the cross-sectional shape, so it is considered that the cross-sectional shape is circular like the invention of Patent Literature 1.